The present invention relates to engine cylinders for a V-twin engine.
V-twin engines typically include, among other things, two cylinders arranged in a V-configuration. Each cylinder typically includes a body having an exterior surface that may optionally have fins (e.g., for an air-cooled engine). The cylinder also includes opposing ends, whereby a cylinder head is disposed on one of the opposing ends, while the other opposing end is received within the crankcase. A cylinder sleeve within the body defines a cylinder bore configured to slidably receive a piston coupled to a crankshaft of the engine via a connecting rod.
Many owners of V-twin engines, including motorcycle owners, look for ways to increase the power output available from their vehicle. Although some may replace the existing engine with an entirely different, larger engine, this can be extremely costly, labor intensive, problematic and time consuming. Thus, many find that upgrading the existing engine is a more viable option. One way in which power output is increased for an existing V-twin engine entails, among other things, upgrading the engine with a big-bore kit to increase displacement. An exemplary upgrade includes converting existing 96 in3 and 103 in3 Harley-Davidson Twin Cam engines to 110 in3 displacement engines by providing replacement cylinders having cylinder bore diameters of 4 inches.
Along with the cylinder bore increase, the outer diameter portion of the sleeve that fits into the crankcase has a similar increase in size. This is because the cylinder sleeve wall thickness of the new cylinder is typically about the same as that of the original cylinder that is removed (i.e., typical wall thickness may be about 0.090 inch for cast iron sleeves) to maintain the requisite sleeve strength. Thus, when replacing original cylinders with larger bore replacement cylinders as previously mentioned, it is also necessary to increase the diameter of the corresponding crankcase bores to which the cylinders are fitted. Increasing the size of the crankcase bores entails removing the crankcase from the vehicle, splitting apart the crankcase halves and machining the crankcase bores to allow fitting of the larger bore cylinders. Although not as involved as an entire engine replacement in some respects, this process is also very labor intensive and time consuming.